Elastic-fluid turbine.



W. L. R. EMMET. ELASTIG FLUID TUBBINB.

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Patented June 15,1909. v

.F'igm Witnesses: lnventor:

William L R .Em,met`.`, f. fai; gm bu WILLIAML. EMMET,'OF SCHENEGTADY, NEW YORK, ASSIGNQR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELAS'lG-FLUID TURBINE.

Specication of Letters Patent.

Patented June l 5,l 1 909..

Application filed February 24, 1909. serial No. 479,697.

To all whom t may concern:

Be it known that I, WILLIAM L. R. EM- MET, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Elastic- Fluid Turbines, of which the following .is a

specification.

This invention relates to elastic fluid turbines wherein the moving buckets are carried by a drum and the stationary or intermediate buckets bythe casing. The object of my invention is to provide an effective means for dividing such a turbine into stages without the use ot' diaphragme, i

illustrative of one of the. embodiments of my inventionJ Figure 1 is a partial axial section of a turbine; Fig. 2 is a detail view of a portion of one of the nozzles and Fig. 3 is an enlarged view ol' the means employed to reduce ea rage.

1 indicates the annular stationary casing` of 'a turbine having an internal shoulder 2 that receives and supports the diaphragm 3.

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.steam to be handled increases.

rIbis casing is split axially as usual to enable the part-s to be assembled. In the shoulder is port l delivering steam to the nozzle 5 supported thereby. This nozzle comprises a plurality of closely associated sections and may be expanding or non-expanding in character.'v The intermediate buckets (3 may be supported in any suitable manner. I have shown each two rows mounted in segmental rings 7 that are let into grooves in the casing. The moving or wheel buckets 8 are mounted on the drum 9 and are. secured as are the stationary buckets by means of channel bars l0 that are let into the drum on one hand and into the rings 7 on the other. Both rotary and stationary bucketsare provided with covers to confine the steam to its proper path and to reduce leakage.

In order to dividethe turbine into stages nozzles 11 are provided whose cross-sectional areas increase by es as the volume of These nozzles comprise an outer ring 12 and an inner f ring 13. Both of these rings are split axially into segments, as many as desired, to enable the turbine to beassembled, and also to permit each of the segments to expand and contract independently of the other or others. The sheet metal nozzle partitions 14 may be secured in place in any suitable way, for eX- ample by casting them into both rings. The nozzle 4, the stage nozzles 11 and the stationary and moving buckets or vanes 6 and 8 coturbme or =that through which the steam Hows as it performs useful Work, t. c., driving the rotor.

In turbines of .the character described there is a difference in pressure more or less great between oppositesides of the nozzle, which difference causes steam to ilow through the clearance between the bore ol said nozzle and the peripheral surface of the drum. It' the parts are 'of large diameter the steam thus lost through the clearances maybe a very considerable item, and seriously affect the economy of operation. .Another factor to be taken into consideration is the unequal due to temperature changes brought about by changes in pressure occasioned by load variations. Also that under certain conditions the peripheral surface of the drum may be caused to rotate slightly out of the path ofa true circle due to springinon or whipping of the shaft or other cause. lIt is also to be borne in mind that the moving buckets are traveling past the nozzle and stationary buckets at a highrate of speed, varying from about 225 feet per second in marine turbines to about 425 feet per second in land turbines.

The troubles incident to distortion and whipping can be largely or entirely obviated by making the clearances large, in which case there is an abnormal leakage of steam accompanied by a reduction in economy. On the other hand, the leakage losses can be greatly reduced' by making small clearances, but here is encountered the diiliculty of insuring tree operation of the parts without contact when distortion, or springing or whi ping of the shaft takes place.' The proilem thus resented is. to provide a means which will have all ol the advantages none of their disadvantages. o meet th ese exacting requn'ements, the ring 13 is made 1n operate to form the working passage of the' distortion of the stationary and rotary parts' of the arrangements above s eciiied with ceases,

a special Way. In reality it comprises two concentric rings an inner and an outer united at one side only and separated at other points -by a space. In its bore are ormay be teeth or projections 15 integral or otherwise,

. each of which presents a relatively narrow` surface to the drum. The end surfaces of the teeth are se arated from the drum by 'a relativelyv sma clearance to reduce leakage. This arrangement of alternate teeth and grooves further acts to retard leakage, A

sim le and satisfactory Way to make these teet is to cut a screw .-thread of coarse itch is somewhat reduced, or'at least is not greatly increased, so that the portion 18 directly carrying the teeth or projections can yield out-v wardly of the drum 9 by undue distortion, springing or whipping of the shaft moves out of its true path and rubs thereon. The crossv section of the inner ring 13 is substantially U-shaped with the legs of the U extending parallel to the drum, one leg forming a suport for the nozzle partitions While the other eg is free to move under the conditions speciied. T he movements referred to herein' measured in fractions of an inch would be very small indeed yet nevertheless they arel of the utmost importance, and provision must `be made to( compensate therefor if the best results are to be obtained.

Another im ortant feature tobe noted is that the meta at 19 which is in direct line with the solid part of the ring is cut back or away from the drum so that it can never be engaged thereby no matter how great the distortions of the drum, casing or parts carricd by one or all of said turbine members may be. In many cases it is also desirable to cut away that portion of the drum directly in line with the solid part of the ring 13, as shown, and for the same purpose. Owing to the fact that the points or ends of the teeth on the ring are relatively thin.. and easily heated, they will in case of accidental rubbing wear away much faster than the drum, and without special injury to the latter. It is to be noted that the annular slot 16 in the ring is somewhat longer axially than is the s ace occupied by the teeth or projections.

his is done so that the part 1S can expand andincrease its diameter when heated, and

'contract and decrease its diameter in cooling without being impeded in said actions. The arrangement also prevents. serious injury when for any reason the drum strikes the teeth or projections at some portion of their circumference and nieves the part 1S bodily at the point of contact.

When the turbine is operating there will be a thin annular iilm of steam leaking axially through the clearance space between the teeth and the adjacent finished surface of the drum becauseit is impossible to cut off all leakage where the parts must be held out of mechanical contact. By means of the arrangement shown I can, however, reduce this to a minimum by vreducing the clearance to a much smaller amount than would be practicable or safe if the inner nozzle rings 13 were made solid. In addition to the small clearance between' surfaces acting to reduce leakage, the grooves between the teeth'also perform the same oflice. The flow of steam is axially and in an annular and very thin vilm and in passing the mouths of the grooves little whirls or eddies are created in said film which act to materially choke back or retard its flow.

Asan additional meansl to reduce leakage buckets may increase in height by suceessive steps instead of gradually. With this arrangement the steam ten ds to pass over the clearances instead of out of them.

By reason .of my improved construction I am able to dispense with diaphragms in certain portions of the turbine, usually the low pressure end, which commonly extends from the casing to a point near the shaft. This results in mechanical simplification in man v cases, reduces the total length of the machine, and reduces the weight of the parts.

If the inner ring 13 was made solid and rubbing took place between the wall hof its bore and the drum, the heat generated at the contacting surfaces would cause the ring to expand and since it is confined by the turbine casing this heating would cause the wall ol its bore to move toward the drum. Abnormal heating ofthe drum would cause it to enlarge and hence thc e'll'ects of the heating would be accumulative and would continue until the metal of the ring. or drum or bot-h commenced to iow. This action would c`ontinue until the contacting surfaces were ac tually separated by' the melting or vllowing of the contacting surfaces. By making the inner ring l?) .in segments and with the capacity to expand outwardly I avoid the very 'great objections noted above and at the sanie time keep the leakage down to a low value. In some cases I may omit the teeth 15 and make the bore of thev ring portion 1S smooth but it is better to use the teeth because they are effective in reducing leakage.

I may use my invention on some or all of Y I desire to have it understood that the apparatus shown is only illustrative, and that the invention can be carried out by other means., What I claim as new and desire to seelre by Letters Patent of the United States, is;-

l. In a turbine, the combination olf-4a casing, a rotor, buckets carried by the casing and also by the rotor, and means-for dividing the casing into stage compartments, which is provided with a leaka reducing means comprising a segmenta` ring the Wall of whose bore is located in closegpnoximity to al surface on the rotor and 'whic is free to expand outwardly under tempera-ture changes.

2. In a turbine, the combination of a. casing, a rotor, buckets carried by the casing and also by the rotor, anda means for dividing the casing into stage compartments which includes a leakage reducing means comprising a segmental ring that is composed of two rincipal portions, one of which is relativelyl` ed in position While the other is supported at one side only and is free to expand outwardly when heated.

3. In a turbine, the combination of a casing, a drum located therein, rows of buckets mounted on the drum for driving it, iiuid directing means arran ed in rows and carried by the casing and located between the rows of wheel buckets, and a means for unitingvthe ends of certain of theiiuid directing means and reducin leakage comprising a ring the surface of w ose bore cooperates with a relatively movable part ofthe turbine, the said ring being separated from its sup# port for a portion of its axial length by a space to permit of the ring expanding outwardly.

4. In a turbine, the combination of a cas-A ing, a drum located therein, rows of buckets mounted on the drum for driving it, stationary buckets carried by the casing and arranged in rows between the wheel buckets,

and a nozzle for dividing the casing into stages and discharging motive fluid against the buckets on the drum, the sai nozzle being annular and provided with a ring which surroundstlie drum is provided with leakage reducing means in its bore and is cut away directly in the back of said means to permit of distortion.

5. In a turbine, the combination of a casing, a rotor located therein, rows of buckets mounted on the rotor for driving it, fluid directingk devices carried by the casing, a structure carried by said devices for reducing leakage and comprising a ring attached to -said evices and'a second ring supported by the first at one side only and separated at other pointsto permit of independent expansion andv contraction, and means on the second ring that coperate with the rotor to reduce leakage.

6. In'a turbine, the combination of a casing, a rotor ylocated therein, rows of buckets mounted on the rotor for driving it, devices carried by the casing forV directing Huid against the buckets, the said buckets and devices coperating to form the working passage, an a means for reducing the effects of unequal distortion and leakage in the working passage of theA turbine conlllprising concentric rings united at one side o y and separated b a space at other points, one of said rings eing supported b one of the main elementsA of the turbine w 'le the other ring is free to expand and contract.

7. In a turbine, the combination of stationary and rotary parts, a' means dividing the turbine into stage compartments an preservin a difference of pressure therein, and a lea age reducing device comprising a segmental ring that is suplported at one end on yand is free to expan an increase 1n temperature.

8. As an article of manufacture, a nozzle structure comprising outerand inner rings, the inner ring being substantially U shaped in cross-section with the legs of the U extending axially, and partitions fordirectin the iuid which connect the. outer and mner rm s.

n witness whereof, I have hereunto set my hand this 23rd da of Februa 1909. WILL AM L. R. ET. Witnesses:

BENJAMIN B. HULL, HELEN Oar-oen outwardly under 

